This is the worst - intermittent starting problems. This is my sons car, purchased from an Audi Mechanic so it was well maintained and completely reliable until recently. Was driving the car a while back pulled to a stop sign and basically just died, wouldn't re-start. Pushed to parking lot left overnight and then started in the morning (cold). Mechanic replaced fuel pump. A few weeks back same deal, drove to practice let sit for two hours wouldn't start, next day started, drove to mechanics, he was unable to make it repeat, replaced pick up coil and fuel pump relay. Yesterday, same deal, only was able to get the car to start after trying 2-3 times, let sit for 15 mins and then started. The only thing that seems consitent is that it has its occasional problems after it has been driven. Anyone with any ideas please let me know-thank you.

 

Classic engine temp. coolant sensor symptom. First start of the day should be succesful, but subsequent starts are either rough or not happening. The sensor gets gunked up, or broken, and can't read temps correctly. So the ecu thinks the engine is cold when it's hot and so the air/fuel mixture is way off (rich) causing hard starts or even stalls. ECTS when bad may not trigger a CEL (didn't for me) but there may be a fault code stored for it in the ECU. If it's not the ects then the next thing I'd suspect is the MAF, but that should trigger a CEL.